1. Field of the Invention
The present invention relates to water-based polyurethane compositions. More specifically, the present invention relates to stable water-based internally-crosslinkable polyurethane compositions containing crosslinkable unsaturated groups.
2. Brief Description of the Prior Art
Water-based polyurethane compositions in the form of solutions, dispersions or emulsions are generally known in the art. One approach to providing water-based polyurethane compositions has been through the use of emulsifiers. The resultant polyurethane emulsions generally suffer from the disadvantages of instability of the polyurethane compositions and water sensitivity of the resultant films. Another approach to providing water-based polyurethane compositions has been through the use of base-neutralized ionizable groups, such as salts of carboxylic acid. The introduction of carboxylic acid into polyurethane polymers can be a problem because the carboxylic acid can react with isocyanate starting materials. This reaction can lead to the reduction in the content of the carboxylic acid of the polyurethane polymers, the destabilization of the polyurethane polymers and the formation of undesirable side products.
Nonetheless, given the environmental and performance advantages of water-based polyurethane compositions, work in this area has continued in an attempt to improve on the performance properties of the water-based polyurethane compositions. By the present invention, there is provided a water-based polyurethane composition with improved performance properties.